The present invention relates to polyol compositions useful in the production of flame-resistant polyurethane foams.
Rigid polyurethane foams are frequently used as insulating materials for insulating against heat or cold. Very thick insulating layers which are gradually being required to satisfy building regulations in many countries present many new technical problems in the construction of buildings.
There is therefore a demand for insulating materials having a very low thermal conductivity combined with high flame resistance.
Polyurethane foams generally have very low thermal conductivity values but it is known that certain polyols or additives provide exceptionally low values. Foams made with 2,4- and/or 2,6- tolylenediamine polyethers conforming to these requirements are described in German Patent Application No. P 3,509,959.
The use of 2,3- and/or 3,4-tolylenediamine (TDA) polyethers has been described in the literature. For example, the use of such polyethers for the production of flame-resistant PUR rigid foams has been proposed in DE-OS No. 2,017,038, U.S. Pat. Nos. 4,209,609, 4,421,871, 4,397,966, 4,562,290 and 4,469,822. These disclosures do not, however, give any indication that rigid foams produced from such polyethers would conform to fire classification B2. The use of polyether polyols based on 2,3- and/or 3,4-TDA for the production of flame-resistant rigid foams is proposed in U.S. Pat. No. 4,410,641 but this patent requires an index range of 150 to 500. The foams obtained at such indices are, however, brittle and frequently unsuitable for use.